<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8">
    <title>Insert title here</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }

        body {
            width: 400px;
            height: 200px;
        }

        div {
            line-height: 100px;
            font-size: 50px;
            text-align: center;

        }
    </style>
</head>

<body>
<!--
<button id="bt_start" >start</button>
-->
    <button id="bt_stop">stop</button>
    <div id="clock_div"></div>
    <script src="js/jquery-3.1.1.js"></script>
    <script src="js/my_clock.js"></script>
</body>

</html>